Boise Weather in September

What's the weather like in Boise (Idaho) in September 2025?

The climate in Boise during September can be summarized as mild and dry.

September is in the fall / autumn in Boise and is typically the 4th warmest month of the year. Daytime maximum temperatures average around a comfortable 25°C (77°F), whilst at night 8°C (47°F) is normal.

Boise weather averages (imperial / metric)
Daytime temperature 25.1°C 77.2°F
Nightly temperature 8.3°C 46.9°F
Average temperature 16.7°C 62.1°F
Daily sunshine 10.8 hrs
Avg rainfall 19 mm 0.7 ins
Rainy days 4 days
Sea temperature 14.5°C 58.2°F
Humidity 45%
Windspeed 13.7kph 9 mph

On average September is the 3rd driest month of the year in Boise with around 19mm 0.7 inches of rain making it a dry time to visit. This rainfall is typically spread over 4 days, although this may vary considerably.

On the flip side this corresponds to an average of 10.8 hours of sunshine per day.

September temperatures in Boise

Boise average temperature in September

September rainfall

Boise average rain in September

September hourly sunshine

Boise average rain in September

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Boise in September 2025.

Other monthly averages

Best places to visit in September

UV index Best time to go?

Beta

Current (hourly) weather 15 day forecast

Boise weather stats

Boise weather statistics
Hottest month: July 31.9°C 89.4°F
Driest month: July 8mm 0.3ins
Sunniest month: July 13.8hrs
Coldest month: January 2°C 35.6°F
Wettest month: November 38mm 1.5ins
Map showing location of Boise (43.6135, -116.20345) Boise map pin © Google

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